The next bit is all touch and feel. Slowly back out the three bolts (15mm IIRC) from the driver's wheel well. DO NOT FULLY REMOVE YET. You can do this without removing the wheel, don't worry about the hub flopping around either way. Once the bolts are relatively loose, hold the power*steering*lines with your left hand and back out the bolts with your right hand. (If you're arms aren't long enough, get a helper) Keep tension on the lines because when that last thread is backed out the*box*will drop. It's 30lbs, so be careful.
Hooray, your box is out. If you didn't drain the fluid through the drain bolt, now is an excellent time to drain the remaining fluid in the box.
Now if you bought a box from me, it will look somewhat like this (EDIT: I've since started painting the boxes and Pitman arms a semi-gloss black to prevent surface rust, so it will look a bit prettier)
The box is locked in the center position with a “locking tool” (in reality it's a M8 – 1mm X 25mm bolt from Home Depot). It comes with the drain plug bolt and a new crush washer. The Pitman arm is disattached.
[If you have sourced a box from other than me it is highly advised that you get a locking screw and use it. Install it by removing the drain plug and, using the input shaft (the smaller one) rotate the box until you can view a hole in the surface of the working piston. Center the hole and thread in the locking tool. Do not overtighten. Torque so that the bolt won't come out and the input shaft cannot move freely.]
Look for the alignment mark on the end of the Pitman shaft (the bigger one).
You want to install the Pitman arm so that the mark on the arm lines up with the one on the shaft.
Install the nut onto the shaft. It will force the arm onto the shaft further. Don't kill yourself, but I like to try to get it to around ½ in to ¾ in from the face of the box. The spines on the arm are drafted and will grip more the further they are on the shaft, the nut is just a retaining nut.
A word on the steering coupling. You can reuse the old one. These buggers are tough, I've cut through a few of them and it doesn't appear that they're going to be able to come apart while driving. So if you have an old cracked one, you can drive with it without fear. I would suggest that you go ahead and replace it now because of the pain of having to replace it later, but to each his own.
DIY for replacement found here:
PeachPartsWiki: Steering Coupling Replacement